1. Field of the Invention
The present invention relates to a fluid pressure cylinder with a position detecting device for detecting the position of a piston.
2. Description of the Related Art
In general, a fluid pressure cylinder has a piston slidingly moving along the inside of a cylinder bore and a piston rod connected to the piston. The cylinder is configured to perform various operations such as transporting, sorting or positioning of workpieces by moving the piston and piston rod to-and-from by the action of the pressure of a fluid supplied into and/or discharged from the cylinder bore. The cylinder is installed in automatic equipment in various fields.
In order to detect the position of the piston and use the detected signal as a control signal for automatic control, the cylinder is configured such that a magnetic sensor (position detecting device) is mounted on an outer surface of a cylinder body using slots and/or rails, etc., formed on the cylinder body, and the magnetic sensor senses the magnetism of a magnet mounted on the piston so as to detect the position of the piston, as shown, for example, in the Patent Documents, Japanese Unexamined Patent Application Publication No. 2002-221204 and Japanese Unexamined Patent Application Publication No. 2006-52744. Therefore, outer surfaces of the fluid pressure cylinder have a complex appearance including many irregularities because of the presence of the above-mentioned slots and/or rails as well as fittings and/or plural attachment bolts, etc., for mounting the magnetic sensor.
However, when irregularities such as slots and/or rails are formed on the outer surfaces of the fluid pressure cylinder, the cylinder is difficult to clean, and dust and/or dirt, etc., may easily collect and remain in the slots and/or rails. In particular, fluid pressure cylinders used for food processing machines are frequently washed using a washing fluid because of hygiene concerns regarding bacteria development caused by residual food, however, if irregularities such as slots and/or rails are formed on the outer surfaces of such cylinders, performance in terms of washing and drainage is diminished, and liquid and/or food debris may easily remain in recesses, behind projections and/or in corners, etc., so that much labor must be expended to remove them completely.
Therefore, fluid pressure cylinders, in particular, fluid pressure cylinders used for food processing machines, are required to have as few irregularities as possible on the outer surfaces, so that they have such a configuration that liquid and/or food, etc., may not easily remain on the surface in order to optimize cleaning in every corner with less cleaning man-hours and in order to obtain good performance in terms of drainage and wiping after washing. It is also important that the magnetic sensor be mounted simply using as few components as possible for facilitating the positioning and/or maintenance, etc., of the magnetic sensor.
However, the above-mentioned conventional fluid pressure cylinders cannot meet the demand satisfactorily because there are many irregularities on the outer surfaces thereof for mounting the position detecting device, and many components including plural attachment bolts are used for mounting the position detecting device.